JPH0311177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flicker compensator connected in parallel with a load in a circuit having a flicker-generating load.

The circuit configuration of the conventional Fritzker compensator is shown in the first example.
As shown in the figure.

1a, 1b, 1c are phase advance capacitors, 2a,
2b, 2c are series reactors, 3a, 3b, 3
Thyristors c, 4a, 4b, and 4c are connected in antiparallel to perform opening/closing control.

1a, 2a, 3a, 4a are No. 1 branches, and with the same configuration, 1b, 2b, 3b, 4b, 1c, 2
c, 3c, and 4c form the No. 2 and No. 3 shunts, and the capacity of each shunt is in the ratio of 1:2:4, and seven-stage control is performed by combining each shunt, and the control is based on the load. 7 is guided from a current transformer (CT) 6 to a current integrating circuit. A pulse signal is sent to the sampling circuit 11 from the potential transformer (PT) 5, phase shift circuit 12, and timing circuit 13, a certain value is held in the detection circuit 14, and a closing command is issued from the selection circuit 15 for selecting the closing branch. , and gate circuits 18a, 18b,
Received at 18c. A synchronization detection circuit 16a that sends out a pulse signal when the thyristor terminal voltage is around 0V,
Signals from 16b and 16c are also connected to gate circuits 18a and 18a.
18b and 18c, and other overcurrent detection circuit 17
Only when the AND of the signals a, 17b, and 17c is established, a signal is sent from the gate circuit, the gate amplifiers 19a, 19b, and 19c trigger the thyristors, and each phase-advanced current flows to compensate for the voltage drop.

Next, the operation of the conventional example will be explained with reference to FIG.

Assuming that there is no response delay in the control section, the charging voltage of capacitors 1a, 1b, and 1c is -√2E.
(V). At this time, depending on the load current (in the figure), the detection circuit 14 sends a closing signal to the selection circuit 15.
Depending on the polarity of the charging voltage, the No. 1 shunt turns ON at the middle point in the diagram with a half-cycle delay.

Also, when the load current increases at the middle point in the figure and the input signal switches from the No. 1 branch to the No. 2 branch, the No.
Branch 1 turns OFF, but branch No. 2 turns ON with a half-cycle delay due to the polarity of the SC charging voltage.

Therefore, the SC current is zero for half a cycle,
It had the disadvantage of generating cuts.

When the load current turns off at the middle point in the diagram, the SC current also
Since it can be turned off, the voltage fluctuation will have two voltage drops.

In this way, SC
There is a response delay when turning on due to the polarity of the charging voltage,
Furthermore, depending on the polarity of charging, it is possible to eliminate response delay, but it has the disadvantage that a break occurs when switching the shunt.

This is because the appropriate capacity is selected after detecting the load current, and the closing command is sent to each shunt, but the closing command is switched without determining the closing status of other shunts at the time of switching, which causes the disconnection. be.

For this reason, even if the response delay was reduced, there was a drawback that the flicker reduction effect was not improved much due to the occurrence of breaks.

In order to eliminate the drawback of the current cutoff that occurs when switching the closing shunt in the dual thyristor system, the present invention determines whether or not the shunt can be turned on after switching when switching the closing shunt before proceeding to the next stage. The purpose of the present invention is to provide a flicker compensating device which eliminates the disadvantage of the generation of cuts and is highly effective in improving flicker by switching the input signal.

The flicker compensator of the present invention will be explained below with reference to the embodiments shown in FIGS. 3 and 4.

Figure 3 is a circuit diagram of the Fritzker compensator.
1a, 2a, 3a are phase advance capacitors, 2a, 2
b, 2c are series reactors, 3a, 3b, 3c,
4a, 4b, and 4c are thyristors connected in antiparallel.

Furthermore, in order to prevent a transient phenomenon from occurring when the capacitor is turned on, the synchronous detection circuits 16a and 16 generate a pulse signal when the voltage across the thyristor is around 0V.
b, 16c are each thyristor 3a, 4a, 3b, 4
b, 3c, and 4c, respectively.

These 1a, 2a, 3a, and 4a are designated as No. 1 branch,
With the same configuration, there are 2 other branches 1b, 2b, 3b,
4b, 1c, 2c, 3c, 4c, each No. 2
Branch, No. 3 branch. Each capacity is 1:2:4
Seven levels of capacity can be obtained by combining each shunt.

Current transformer (CT) 6 controls the current of load 7 as a control unit.
The voltage is detected by the current integrating circuit 10 and the sampling circuit 11 converts it into a DC voltage. Also, a potential transformer (PT) 5, a phase shift circuit 12, and a timing circuit 1
3 to the sampling circuit 11 causes the detection circuit 14 to hold the detected value, and the selection circuit 15 selects the input branch and sends out a signal, which is sent to the determination circuits 20a, 20b, and 20c. The determination circuits 20a, 20b, and 20c receive signals from the synchronization detection circuits 16a, 16b, and 16c other than the shunts, and determine whether or not the other shunts can be turned on when switching the closing stage. Judgment circuits 20a, 20b,
A closing signal is sent from 20c to the gate circuits 18a, 18b, 18c, and the synchronization detection circuit 16 of the branch
Signals from a, 16b, 16c are also sent to the gate circuit 18
a, 18b, and 18c. Further, signals from overcurrent detection circuits 17a, 17b, and 17c are also sent to gate circuits 18a, 18b, and 18c.

In the gate circuits 18a, 18b, 18c, when the logical product of the input signal, the signals of the synchronization detection circuits 16a, 16b, 16c, etc. is established, the gate amplifier 19
a, 19b, and 19c as a closing signal to trigger the thyristor.

Next, the principle of operation will be explained with reference to FIG.

Figure 4a is a load current and power supply voltage waveform diagram, b
is a waveform diagram showing the load current amount as a DC component, c is a waveform diagram of the No. 1 shunt closing signal from the selection circuit, d is a waveform diagram of the No. 2 shunt closing signal from the selection circuit, and e is a waveform diagram of the No. 1 shunt closing signal from the selection circuit. Signal waveform diagram sent from the road determination circuit, f is No.1,
Pulse signal waveform diagram sent out from the synchronization detection circuit of No. 2 branch, g is the leading phase current i _c1 of capacitor 1a,
Waveform diagram h is a waveform diagram of advanced phase current i _c1 of capacitor 1b,
i is a waveform diagram of the composite current i _c1 +i _c2 , and j is a voltage waveform diagram equivalent to a voltage drop.

In Fig. 4a, E indicates the power supply voltage, and _iw indicates the load current.The load is applied from the middle point in the figure, detected by the current transformer, and transferred to the No. 1 branch by the selection circuit 15.
Assume that a closing command is sent as shown in FIG. 4c.

At this time, assuming that the phase advance capacitor 1a is negatively charged, the pulse signal from the synchronization detection circuit 16a sends out a synchronization pulse when the power supply voltage E is near its true peak, as shown in FIG. 4f. There is.

Thyristors 3a and 4a are turned on from point c where the above-mentioned closing signal c in Figure 4 and this synchronization pulse match.
Then, the leading phase current of No. 1 branch flows.

Furthermore, when the load current increases approximately twice from this point and the delayed reactive power also doubles, the selection circuit 15 sends a signal to the No. 1 branch to the No. 2 branch as shown in Fig. 4c and d. can be switched.

However, the No. 2 branch, like the No. 1 branch, sends out synchronizing pulses as shown in Figure 4 f, assuming that the phase advancing capacitor 1b is negatively charged. Therefore, the No. 2 branch cannot be turned on at the time the input signal is switched.

In such a case, the No. 1 branch judgment circuit 20a continues to issue the closing command, and after receiving the synchronization pulse from the No. 2 branch synchronization detection circuit 16b after half a cycle,
The closing signal of the No. 1 branch is turned off, and at the same time, in the No. 2 branch judgment circuit 20b, the thyristors 3b and 4b are turned on by the synchronizing pulse and the closing signal, and a phase-advanced current is caused to flow from the point h in Fig. 4. When viewed as a composite, it flows continuously without any breaks as shown in Figure 4i.

However, even though the load current iw has increased from the point, the leading phase current is delayed by half a cycle due to the polarity of the charging voltage, and a voltage drop occurs as shown in Figure 4 j, but a discontinuity occurs as in the conventional example. Compared to the above, the fritzer improvement effect can be significantly improved.

In addition, in the above-mentioned embodiment, switching from No. 1 branch to No. 2 branch was described, but switching from No. 1 branch to No. 3 branch and from No. 2 branch to No. 3 branch was described. The same can be done for shunting and so on.

Further, the same operation can be performed using a triax having the same function as an anti-parallel thyristor.

According to the present invention, even if the capacity changes frequently during load energization, there are many welding machines, and the capacity is frequently switched due to various overlapping currents during energization, the flicker improvement effect is high.

As described above, the Fritzker compensator of the present invention has the following features:
By taking advantage of the high-speed response of both thyristors and eliminating the break that occurs when switching the shunt, it is possible to improve the flicker reduction effect compared to the conventional method, which is of great industrial and practical value.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of a conventional flicker compensator, FIG. 2 is a waveform diagram of each part of the conventional flicker compensator, and FIG. 3 is a circuit block diagram of an embodiment of the flicker compensator of the present invention. FIG. 4 is a waveform diagram of each part of the flicker compensator of the present invention. 1a, 1b, 1c: phase advance capacitor, 2a,
2b, 2c: Series reactor, 3a, 3b, 3
c, 4a, 4b, 4c: thyristor, 7: load,
15: selection circuit, 16a, 16b, 16c: synchronization detection circuit, 18a, 18b, 18c: gate circuit, 20a, 20b, 20c: determination circuit.

Claims (1)

[Claims] 1. In a fritsker compensation device in which multiple groups of shunts each consisting of a phase advance capacitor, a series reactor, and a semiconductor switch are provided in parallel with the load, and the shunts are controlled to open and close, the voltage at both terminals of each semiconductor switch is around 0V. A synchronous detection circuit that generates a pulse signal at the synchronous detection circuit, a selection circuit that detects the load capacity, selects the input shunt, and sends out the input signal, and a synchronous detection circuit that detects the signals of other shunts other than the input shunt. a determination circuit that receives the input signal from the circuit and continues to hold the input signal of one branch until a synchronization pulse of the other branch is generated when the input branch is converted from one branch to another; A flicker compensator comprising a gate circuit that receives signals from the determination circuit and the synchronization detection circuit and sends a gate signal to a semiconductor switch, and controls the current without interruption when switching shunts.